reason you cannot bring liquids on to a plane. the reason you have to buy little bottles of shampoo and dump ott your water is because of this. the summer of 2006, a group of terrorists with links to al-qaeda planned to board a bunch of different planes at heathrow in london. to be flying from there to the united states and the way these guys were going to bomb the planes was by bringing soda bottles on board those planes that looked like they contained just soda or water, but in fact, they contained hydrogen peroxide and the other components needed to make bombs. the heathrow guys got caught before they did it, but it is now thanks to them that we have to buy humiliatingly tiny toiletries like this hair goo, right?

it's not just security in this case. it's for a reason. hydrogen based bombs. the london bombings of 2005, those were al-qaeda linked terrorists and those were hydrogen peroxide based bombs. those killed 52 people. four years later, there was an american copy cat. in 2009, a guy tried to buy a bunch of hydrogen peroxide from beauty stores near aurora, colorado. it led to the arrest of this guy. he was going to do it in new york instead. on the subway. again, his plan was hydrogen peroxide. they're associated with different groups, taught by specific means and being able to get specific at the type of bomb used both gives investigators something to look for in terms of looking for how and when that bomb was made, but it also gives

them an investigatory thread to pull in terms of the bombs authorship, how the bomber might have learned to make that bomb or who the bomber might have learned it from. sometimes, it works that way. and sometimes, that is the way they stop plots ahead of time. sometimes, that is the way they find the bombers there after. but we learned today from investigators in boston that bombs detonated yesterday afterwere bombs that had a signature, that is the kind that might be much harder to read. >> what we're told by authorities is that they are crudely made. they appear to have been assembled inside a pressure cooker, nd inside a pot like this. assembled the device. it includes a low power explosive. >> now, we have a little bit of new information.

actually, just in in the last couple of minutes from nbc news on this specifically. and i want to tell you what nbc has told us. sources involved are telling nbc news that the pressure cooker bombs in boston were designed and placed to act quote like a homemade clay moor, a powerful directional antipersonnel device, so they don't spray in 360 degrees. they're directional. so these sources are telling nbc news, these and other sources, the triggering mechanism appears to have included a battery pack and a circuit board, elements of a sophisticated triggering mechanism. quote it appeared to be built from scratch, but with a sophisticated triggering mechanism. all bombs are crude devices and it is the way they are triggered that can be sophisticated. they functioned as designed.

pressure cookers are exactly what you are thinking. they are metal cooking pots that clamp the top down tight with a tight seal allowing you to cook food faster under pressure with a normal lid like a normal pot. if it sounds like i am not a person who cooks, you're right. to make a bomb out of a pressure cooker, you need a flammable sub tans to put inside it, but it is the fact that the pressure cooker can be tightly sealed, it means when you ignite that material inside the cooker, it doesn't just bern like if it were out in the open, it goes boom. it explodes and then the metal from the pressure cooker becomes shrapnel that can kill people around it. it is a concept that the idea of a pressure cooker that's been used by bombers. before the coordinated attack in

mumbai, involved multiple grenade attacks, two years before that attack, there was another very horrible attack in mumbai. seven coordinated bombs going off within ten minutes of each other on commuters trains. it was a huge attack. seven bombs all made out of pressure cookers. 290 people were killed. by the time of that monstrous attack, the department of homeland security had put out this bulletin on the potential terrorist use of pressure cookers. noting the bombs has been used in plots in nepal and in france and before the bombings in india and another incident. department of homeland security with that bulletin showed this picture of soldiers in ma lay sha with a bunch of pressure

cookers. this is a website from a pennsylvania company that makes inert explosives. so, not explosives that are going to explode, and they make them for draining purchases. they build products that look like and act like bombs and trigger switches so that law enforcement and the military can train on how to recognize them and detect them and avoid tripping them. to learn how to disarm them. this company sells not to the general public, but to agencies, specifically sell, dummy pressure cooker i.e.d.s to train on because there are so many of them around, it's the kind of thing around that people who work in explosives need to know how to do. people put explosives in pressure cookers and blow them up not using a fuse an a timer, but a gun shot. you can see it on youtube.

pressure cooker bombs are the kind of thing that have been around for a long time that people believe they can make relatively easy. three summers ago, you might remember our coverage of al-qaeda releasing a magazine that tried to inspire home grown terror attacks around the world. their first issue included an article called how to make a bomb in the kitchen of your mom, which was hilarious on one hand, on the other, it gave specific instructions on how to make bombs. what we're told is the type of bomb that blew up in boston yesterday does not seem to be an al-qaeda signature bomb. it's a bit of a u bik wiitous bomb used all over the world by all different kinds of bombers for a long time. a bomb that al-qaeda has made deliberate efforts to make sure it is accessible to anybody, but it is one that has been around for a long time in a lot of

different places. look, there are a lot of bombings in the world. there wouldn't need to be companies in scranton, pennsylvania making fake bombs to train on, but bombing attempts do not usually succeed. we are used to attempted bombings that get towards or that fizzle. since 9/11, the new york city hydrogen peroxide bomb, there was a bomb in a backpack packed with fishing weights. it was discovered before it went off. there was the guy strapped with explosives who stormed the discovery channel in maryland. he was killed by police. the attempted underwear bomber, shoe bomber. there have been lots of attempts to bomb the u.s., but almost no successful bombing attacks, one in which the explosives actually

detonated and caused the intended damaged. there was a small homemade bomb in wisconsin last year. it broke up the window sill. a mail bomb sent to the university in scottsdale, arizona in 2004. it hurt the man who was the sbepded target, but other than those, attempts at setting off bombs in the united states since 9/11, there have been a lot f tries, but they have almost never been successful. an uncomfortably large number of people, almost nobody pulls it. does it say something important about the person or persons who bombed the boston marathon, that they were able to successfully detonate bombs when almost every other plot in recent years has been tharted? and now that authorities tell us it was a pressure cooker bomb,

is that a type of bomb that is too u bik wiitous, too widely understood to be able to point investigators in a specific direction in this investigation? joining us now is dawn, a veteran of the fbi. assistant special agent in charge of the new york joint terrorism task force. chief operating officer of the strategic consulting agency. so, i don't know anything about the subject of bombs. did i say anything in that lead up that struck you? i think. >> i think you were spot on. it's not a unique phenomenon. it's none the less effective. you pointed out the difference between the bombs we saw for the

plot where these, this person went and had specific training in pakistan, afghanistan, learned how to make the concentrated hydrogen peroxide and was going to use that as a main component. that takes training and a bit of practice, which he did, he practiced in denver, then came to new york. that was thwarted because of good intelligence. these are materials readily available. one of the things that will be interesting, what was the charging mechanism? circuit boards and timers and setting a directional charge. these are some of the things that add a degree of sophistication to a bomb that's otherwise crude. normally, you can take one of these devices, set it up, get an egg timer, a battery and wire and relatively crude and set it

and walk away and if you wired it right, it will explode, but depending on what components are are found, some advanced circuitry may mean there's a level of training this person had. i guess the folks will be able to know in short order. >> what we've heard is that the evidence related to the bomb has been taken to the terrorist explosive device analytical center. tdak. what happens there? >> they'll try to compare this bomb, the signature of this bomb to try to find there are similarities, they will try to get a almost, bombmakers tend to follow a pattern. they'll try to do details analysis. they may find a wire. when they look at that wire, it's going to have a set of marks.

down the road -- when they find a pair of wires. they can take the wire cutters, these wire cutters -- a person or a place to a particular device, there's a lot of investigative leads. >> obviously, you're not directly involved in this investigation in boston. if you put yourself in the mind set of an investigator who was heading up joint terrorism task force looking into this, would you have been hoping for a more exotic weapon? would that have been easier to trace? >> a more exotic weapon that was effective would have probably killed more people, so thankfully, you know, the loss of life and certainly don't want to minimize a people that were

killed, but if it was a bomb made with higher explosive set in a different place where the sharp nell was going higher, we could have seen a lot more deaths and serious injuries, so i think -- >> uniqueness of this, this is not a unique, the type of structure. >> the more kind of plain jane it is, the more readily available the materials are. the harder it's going to be to backtrack specifically to where was this pressure cooker or pressure cookers purchased. where was this circuit breaker obtained. the more plain vanilla it is, it makes the search more wider. >> it's really helpful to have you here. love to talk to you again about this. in terms of the latest information, some of the basics are the same as they were yesterday. but some information has shifted

in the past 24 hours. the confirmed death tole is tree. we can name two of the three who were killed. they are 29-year-old krystle campbell of medford, massachusetts. she had been at the finish line yesterday to cheer on a friend who was running. 8-year-old martin richard, he was in the crowd watching the marathon with both parents, his brother and sister. his mother and sister are critically injured. his father released a statement, my dear son, martin, has died. my wife and daughter are both recovering from serious injuries. we thank our family and friends, those we know and those we have never met for their thaukts and prayers. the third victim, a boston university grad student from china. the name has not been released. pending permission to do so from the family. and we will honor that absolutely. of the three who were standing together, one was killed, one

was unharmed and the other was injured and is now in stable condition and boston medical center as of tonight. of the 176 injured, 71 of the wounded remain hospitalized. of the 71, 24 are in critical condition. boston medical center has 19 patients. the hospital said the majority of them will require further surgery. brigham and women's hospital has 15 patients. five critical. mass general has 12 parnlts, eight critical.

beth israel, boston children's has two, and at tops, ten patients. thankfully none with life threatening injuries. investigators have still closed down a crime scene that measures about one square mile. it's a roughly triangular square mile, but that's how much ground they are pouring over. janet napolitano, the fbi director, robert muller and nsa director, keith alexander, briefed members of the house and senate agencies this afternoon. in terms of what bostonians are doing, there have been vigils and public events. the largest taking place at boston commons. 8-year-old martin richard was remembered tonight at a vigil in his local parish church. doors were open for official vigils tonight. the st. james in somersville, doors are open. the church in boston proper, st. paul church, there are events at boston university and brandice university. gathering for a vigil for the victims as well as a vigil for the -- itself.

the white house announcing today that president obama will travel to boston the day after tomorrow to speak at a service at boston's cathedral of the holy cross. the president branding the attack as an act of terrorism, but officials don't know quote whether it was planned and executed by a terrorist ors, foreign or domestic, or the fact of a malevolent individual. finding out -- that law enforcement is poring over as we speak. what officials are trying to get from the public, that's next. for those nights when it's more than a bad dream, be ready. for the times you need to double-check the temperature on the thermometer, be ready. for high fever, nothing works faster or lasts longer. be ready with children's motrin.

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one of the first things the investigators said to the public, we need your help. anyone who has information along the posten marathon route and elsewhere, send us whatever information you have. no piece of information or detail is too small. >> we would like to review any kind of media that you have out there. that might give us additional leads. >> the person who did this, as for anyone who may have heard someone speak about the marathon or the date of april 15th in any way that indicated that he or she may target the event to call us. has received more than 2,000 tips today, many of which are have been vetted. >> there were thousands of pictures taken yesterday before,

during and after the bombing. investigators saying they want all of it. do not self-sensor, do not hold back. send in everything. in addition to calling 1-800-call fbi, they can call any local boston police precinct and report information anonymously. authorities keep stressing no piece of information is no niece pees of information, no detail is too small. when you think about it, that means they are not trying to avoid being overwhelmed by a flood of information. they are in fact asking for a flood of information and getting it. >> the response has been amazing. pardon me for using a geeky computer term, three terrabites. i'm not sure how many still pictures that would be, but needless to say, it's a huge amount of material and they say they're going to look at all of it. they're asking people who flew into the airports, people that they want to share. so they ask repeatedly during this morning's news conference for pictures and skills. they believe that's a very, very source of evidence for them and they are pushing hard to get pictures. >> by asking people for everything, by asking for people to send in everything related to

i'm not sure how many still pictures that would be, but needless to say, it's a huge amount of material and they say they're going to look at all of it. they're asking people who flew into the airports, people that they want to share. so they ask repeatedly during this morning's news conference for pictures and skills. they believe that's a very, very

source of evidence for them and they are pushing hard to get pictures. >> by asking people for everything, by asking for people to send in everything related to the bomb x, they're not worried about getting overwhelmed. that they have the ability to mind this data and will make something useful of it. are they right? joining us now is an msnbc national security analyst. michael, thank you for being here. >> good to be here, rachel. >> i feel like asking for all the information in the world is is asking for so much information that you can't conceivably get anything that might be useful. why are they so confident they can data mine this stuff? >> they're not going to do it perfectly. if you look at what happened in london 2005 when they had bombings, there were hours and hours of videotape. it took the british months to

get through that. the fbi and u.s. intelligence community is better than that. technology is advanced. they're going the start as close as possible to the event, to the explosions and move out from there. so, my nat data first and then slowly but surely, they'll get through the rest of those photos and video. over time, but it will be weeks. they will have a better sense of what might be connected to other factors, like the bags that they think carried the bombs. so i think it's great, get this now, because it's difficult to be preserved. >> is this, is that an approach that has evolved over the past 12 years? is that not the way they would have approached this before 9/11? before we had this huge investment in intelligence since then? >> first, we simply didn't have access to all this video and photo technology that is ubiquitous today.

there are far more video cameras, hoemts and restaurants and people are walking around with iphones. the second is a much greater ability to deal with these massive amounts of data and the technology there has improved and the u.s. government and the intelligence community has been on the forefront. >> is there a risk they're asking for too much? you think about the sort of assessments we made in what went wrong in missing 9/11, the warnings that happened ahead of time. is there still a risk? >> there's a risk they're going to get lost with too much, but it's outweighed. otherwise, they'll never have it. restaurants, hotels, routinely delete these recordings after a couple of days or a week. they've got to get it now, preserve it and eventually, they'll get to it. >> we just got new news tonight

through nbc, sourcing telling nbc that the triggers mechanism on the devices, while that may not have been the world's most sfes kated bombs, they may have been more sfes kated than previously led to believe. is that important? >> i think it's mostly because circuit boards could be more easily traceable than other components. ball bearings, they're pretty common. backpacks, maybe similarly so, but circuit boards generally so some signatures that you can track back to a specific item where it was made and purchased. >> it doesn't necessarily indicate something specific about the bomber, but it could help you find it. the most sophisticated device is one that works and that is where these guys or this person succeeded. >> i am supposed to good night you right now, will you stay and

i'll pay you or something? >> i think you do any way. >> good. hold one moment. corporate masters. we have to pay them a little bit more. we'll be right back.

this is a picture of castor beans from castor beans comes castor oil, which has many uses, if you must know, as a laxative. when you mash the beeps to get castor isle oil, there is a

number of of deadly products including ricin. you can acquire one component of one of the most famous do it yourself poisons. it is at least makeable with things that are not illegal to obtain in their initial state. with the country glued to the boston marathon, late this afternoon, news broke that a letter sent to the office of mississippi senator roger wicker was screened in an off site mail facility br it reached the capitol and tested positive for ricin. it is now being tested by the fbi to make sure it was not a false positive. none of the workers were exposed to the poison. joining us now because i made him stay, michael, do you have any perspective for us on what a test for ricin is and whether or not this is something to werery

about? >> there's the initial screening, that proved positive. there's a lab test. what i would stress is that false positives in those first two are relativity common. it doesn't mean that we don't have to be concerned about that, but in my time as the director of the national counterterrorism center, we saw fairly routinely false positives. we have no idea what the lab test is going to say, but is ricin one of the things that more frequently gets false positives than other things that we hear about? >> it's fairly common. we've seen more ricin than we do with anthrax, but powder in letters is a very common occurrence. people don't hear about it muff,

but it gets a lot of publicity. >> i owe you. thank you for staying. we'll be right back. [ male announcer ] why is kellogg's crunchy nut so delicious? because every flake is double-toasted... splashed with sweet honey... and covered in rich double-roasted peanuts. mmm. [ hero ] yummy. [ male announcer ] kellogg's crunchy nut. it's super delicious!

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if you are not a person who runs marathon, one of the jarring things is that it is mostly full of ads for other marathons. so like the kansas city marathon, which is about running a marathon and eating barbecue. the bermuda marathon in january. six different half marathons in six different american wine country regions. there is a ladies only marathon at niagra falls where they put in the ad that the potties are really nice that since there's no men in this race, they can pick flowers. you can forget if you're not a runner, that marathon running is a whole big culture and industry and that if you are going to run something like the boston marathon, it is likely the case you have been training your life to do this race once. you are quite likely someone who is going to do it again.

a lot of people run 26.2 miles as often as they can. so often they have a preference on the potties. in the days immediately after 9/11, new york city stepped up security in a really visible way. there were soldiers in the train stations carrying military rifles. they stopped playing baseball everywhere in america after 9/11. when the games resumed later that month, you had to go through new security checks to get into the stadiums and at first, it took a long time because the extra checking was new and we are not yet good at it, but at least a baseball stadium is in a contained place. a stadium seemed like a place you could make secure if you we want through enough trouble. new york city even hosted a world series after 9/11 that year. but something like this, like marathon route. it's 26 miles long.

this is not so easily locked down and secured. these pictures are of the new york city marathon which happens every year in november. in chicago and fargo and bermuda and where ever, they tend to be open events. crowds crowd in close. they slap runners high fives. offer the runners water and orange slices. in 2001, new york city had a few weeks to figure out whether or not they were going to hold this kind of race. across 26 open miles right after 9/11. >> sunday is the new york city marathon, 30,000 runners, over 100,000 spectators. can an event of that size be protected? >> darn right it can be, just the way the three world series games will be. >> can you tell us what kind of

security you have in place? >> a lot. we never tell the kind of security we have in place. >> what kind of security for the marathon? a lot and no, whether he not you what it is. after 9/11, runners be warned not to take the orange slices and water from strangers along the route as a security precaution. new york city held its breath and the runners shoved off from staten island and into central park. the race came off great, safely. we do not yet know why the boston marathon was attacked yesterday, killing three people, injurying more than 170 people. it could have been chosen as a site that would be guaranteed to f a lot of people. a symbol. patriots day in massachusetts. there was tax day for the county. this week has any number of other anniversaries. it could have been an attack on boston specifically. it could have been an attack on

america generally and this is just where it happened to hit, but in the immediate sense, what happened yesterday was an attack on the highest profile moment of the highest profile event of a relatively pro file culture. the marathoners, the endurer, addictive contenders doing something that's not much like anything else in our culture. marathoners are after a gratification not just delayed, but a form most of us have a hard time believing can be gratifying. but that difference fosters fellowship among marathon runners and that has fostered culture and now, even a whole economy you wouldn't know existed unless you went looking. this is a runner named ambi burrfoot. he won the marathon in 1968. he was less than a mile from the finish yesterday when the explosions put there.

it is hard to believe this attack targeted the marathon, but even if it was hit as a symbol of something else, it was hit in a way that mean it is world to a whole community of people who run. he wrote today in runners world, this wasn't just an attack against the marathon. it was our use of the streets. we have used our public roadways for annual parades, protest marchers, marathons and all over manner of events. the roads belong to us and their use represents a part of our free and democratic tradition. i trust and believe that will not change in the future. not in boston, not at the boston marathon and not in other important event. we cannot tent violent akts koent threaten our great institution, but our institutions did not become

great by following a path of timidity and cowardess. we can only hope it will rise again stronger than ever. joining us now is ambi, who celebrated his 45th anniversary of winning yesterday. three quarters of a mile yesterday when his wife called him with the news of the bombing and he is editor at large of "runner's world" magazine. thank you so much for your time. fz. >> thank you very much, raf el. >> is that your finisher's medal? >> this is, even though i did finish, i was stopped at three quarters of a mile from the finish yesterday. we were able to pick up our bags and medals today. i'm not wearing it for myself, but really to honor those people who we lost yesterday and who were so injured yesterday. they were in that particular location for only one reason.

because they were supporting the marathon and us runners and that makes them part of our family of runners and we want to remember and honor them. with this medal, with all of our medals and our thoughts and prayers. >> when i saw you writing today, that the attack yesterday was an attack against the democratic use of the streets, wanted to ask what that means to you as a runner and what that means to all of us more broadly as we were thinking about how to respond to these attacks and not be terrorized by them. >> well, i was writing that not primarily as a runner because i've been running through the streets of america for more than 50 years. you begin to generalize for a larger picture and i began to think, you know, these races, they're not sporting events like thred sox and patriots. they're more like a july 4th parade or a civil rights march

or street theatre. i feel americans have the right to enjoy and use and discourse in our great streets and great squares. the boston common just in my backyard, these are important places for us to go to safely. >> as a marathoner, somebody who's been so involved in what seems at least from the outside like marathon culture, not even sure if that's the way you think about it. i top out at two miles, then i fall down. as somebody who's been so involved for so many decades, when you think ahead about the future here, do you imagine these events lki we try to fetye the kind of joy these events are associated with for you we're thinking about that now and in the fall, we had hurricane sandy canceling the new york city

marathon at the last moment. it is weighing heavily on our minds now. there are going to be people, let's face it, great runners, who are going to decide not the spend 3 or $4,000 across the country to a big marathon where they might feel threatened, but i've talked to a lot of runners in the last 24 hours and i would say 99% of them, including myself, are more resolved to come back to boston to run it next year an we have been before because we want to reclaim the city and the streets and we want to thank the city and its supporters and rooters who have been so much in our background and supporting us through the years in this wonderful event. >> winner of the 1968 boston marathon. thank you for being with us tonight. i really appreciate it and what you wrote today i think reached

a lot of people who wouldn't otherwise be reading, but i think what you wrote today meant a lot. thank you. all right. while the tragedy in boston yesterday has dominated today's news, some very important politics are underway in washington and it turns out tomorrow is going to be a big deal, a big "d" deal tomorrow in washington. we have that next. card hassles?

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as the country's attention stays focused on the after math of the bombings, washington is paying attention to the background checks for gun sales vote. right now, a clear majority of the united states senate supports the toomey amendment. 62 senators on record for it. 40 on record against it. that should be great news for people who want background checks, right? after newtown, it's got clear majority support to expand background checks. except the republicans are filibustering it so majority won't matter. the 40 senators who are voting no are not committed to voting against the background check. they are voting against there

allowing to be a vote on the background check on the amendment. they are voting to filibuster. a majority is voting in favor, so they are going to try to block the up or down vote. jeff flake waited until the coverage of the bombings last night to announce, quietly, silently, in fact, on his facebook page that he will vote against background checks. eight in ten of his constituents in arizona support background checks. he said last night or rather wrote to facebook last night that he's going to vote no. he's voting to filibuster, quietly. that was last night around 9:00 p.m. hey, arizona senator, jeff flake showing up to dedicate a room to gabriel zimmerman.

he was an aid to congresswoman gabby giffords. she was shot in the shooting in january 2011 where congresswoman gabby giffords was shot. he was killed trying to protect gabby giffords. senator flake showed up, spoke alongside gabby giffords and mark kelly at that event. these two spent the day rallying for the background check on capitol hill. jeff flake will block it from even getting voted on, thus far at least. the republican filibuster is due for its test tomorrow afternoon. watch this. [ female announcer ] are you sensitive to dairy?

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we have new pictures and new details this hour about the devices that were detonated in yesterday's attack at the boston marathon. we did not have them at the top of the hour, but we have them now. this is what is left from one of the bombs investigators recovered. according to a homeland security document, definitively one of the bombs consisted of a pressure cooker concealed in a backpack. here is a picture of what may be the backpack. they are saying while the second device was housed in a metal container, there's insufficient evidence to determine if it was also a pressure cooker. the fusing system for the two devices are unknown at this time. this also appears unclear if what you are looking at in this picture is the pressure cooker device as it seems or maybe it's the we're not quite sure it was

a pressure cooker device, but this is what they are showing us of what is left over from the bombs. we learned over the last hour, they each contained tiny nails. nails that are smaller than the ones you would use to hang a picture, more like brads or fine nails according to a person assigned to the case. the devices themselves appear to have been delivered in two bags. sources told nbc the triggers mechanism on one bomb included a battery pack and a circuit board. elements that have been recovered at the scene. that's important. a sophisticated triggering mechanism, michael leiter telling us of lesser importance in narrowing down the suspect in terms of expertise and training but more important to give clues to trace to the source to find out how the bomb was assembled and where the pieces came from that allowed the bomber to put